1. Field of the Invention
This invention relates to an electrophotographic type image formation apparatus such as an electrophotographic copying machine, a laser printer, a laser facsimile, an electrostatic recorder and the like.
More particularly, it relates to an image formation apparatus for forming an image (or picture) through an image formation process including the step of charging the surface of an image carrier such as an electrophotographic sensitive body and an electrostatic recording dielectric.
2. Description of the Prior Art
Recently, a conventional image formation apparatus such as an electrophotographic copying machine, which employs an electrophotographic system, includes a contact-to-charge means such as a charge roller, for the purposes of achieving a low ozone emission and a power saving.
The contact-to-charge means is operated to contact under a predetermined pressure the surface of an image carrier in order to charge the surface. For example, the charge roller, which is held in contact with the surface of the image carrier, is rotated together with the image carrier to uniformly charge the surface of the image carrier with an electric potential.
Of all the image formation apparatus of this type, there is one which is of a unit construction, having a process cartridge removably mounted on the main body of the apparatus and adapted to contain an image carrier and attachments thereof, chiefly for the purpose of achieving an easy maintenance.
In an image formation apparatus disclosed in Japanese Laid-Open Patent Publication No. Hei 3-130787, a charge roller serving as a contact-to-charge means is located on the apparatus body such that when a process cartridge is attached to the apparatus body, the charge roller is faced with the surface of the image carrier.
Also, with respect to the contact-to-charge type image formation apparatus, various proposals (invention) are heretofore made in order to prevent inferior charge.
For example, Japanese Laid-Open Patent Publication Nos. Hei 53-130787 and Hei 5-188738 disclose inventions in which a cleaning member is brought into and out of contact with the surface of a charge roller to remove foreign matters attached to the surface of the charge roller so that a uniform charging is realized.
On the other hand, in the event that a remaining toner is adhered to the surface of the carrier itself, there is a possibility that the remaining toner adheres also to the charge roller to thereby invite inferior charge.
In view of the above, there is heretofore known a type in which a carrier cleaning means, such as a cleaning blade, is brought into contact with the surface of the image carrier in order to remove the remaining toner on the surface of the image carrier on the upstream side of the charge roller by this carrier cleaning means.
As one example of this type, there is known an arrangement in which a cleaning blade is located on the upstream side of the contact area of a charge roller, so that the cleaning blade is brought into contact under a predetermined pressure with the image carrier to scrape off the remaining toner on the surface of the image carrier with the edge of the cleaning blade.